Tankless water heater box



FIG. 1 is a front elevation view of a tankless water heater box showing our new design;

FIG. 2 is a right side elevation view thereof, the left side view being a mirror image;

FIG. 3 is a top plan view thereof, the bottom view being a mirror image; and,

FIG. 4 is a rear elevation view thereof.

The ornamental design which is claim is shown in solid lines in the drawings. 

We claim the ornamental design for a tankless water heater box, as shown and described. 